1. Technical Field of the Invention
The present invention relates to a mounting structure for a semiconductor device (hereinafter referred to as an “IC”), an electro-optical device using the mounting structure, and an electronic apparatus using the electro-optical device as a display. More particularly, the present invention relates to a terminal structure in a mounting structure, using an anisotropic conductive film.
2. Description of the Related Art
Liquid crystal devices are typical of electro-optical devices. For example, in a passive matrix liquid crystal device 1 shown in FIGS. 1, 2, and 3 among the liquid crystal devices, a first transparent substrate 10 made of glass or the like and a second transparent substrate 20 similarly made of glass or the like are fixedly bonded with a predetermined clearance therebetween so as to hold a sealing material 30 therebetween. Between the first transparent substrate 10 and the second transparent substrate 20, liquid crystal 5 is sealed in a liquid crystal sealing region 300 enclosed by the sealing material 30. The first transparent substrate 10 and the second transparent substrate 20 are provided, respectively, with electrode patterns 15 and 25 for driving which extend in orthogonal directions so as to apply voltage to the liquid crystal.
In the liquid crystal device, since the second transparent substrate 20 is larger than the first transparent substrate 10, a portion thereof protrudes from the edge of the first transparent substrate 10. The protruding portion 200 of the second transparent substrate 20 has an IC mounting region 70, where a driving IC (semiconductor device) 7 for outputting driving signals to the electrode patterns 15 and 25 is mounted, and a flexible wiring board connecting region 80 that connects a flexible wiring board 8 for supplying various signals and voltages to the driving IC 70.
The electrode patterns 25 formed on the second transparent substrate 20 extend from the IC mounting region 70, and signals are directly supplied thereto from the driving IC 7 mounted in the IC mounting region 70. In contrast, the electrode patterns 15 formed on the first transparent substrate 10 are electrically connected to the ends of wiring patterns 94 for conduction between the substrates, which extend from both ends of the IC mounting region 70 of the second transparent substrate 20, via an intersubstrate conducting material contained in the sealing material 30 when the first transparent substrate 10 and the second transparent substrate 20 are bonded by the sealing material 30.
In this example, the IC mounting region 70 and the flexible wiring board connecting region 80 are generally structured as shown in FIG. 9 as a partly enlarged view. In the IC mounting region 70, an electrical connection is made between the driving IC 7 and the wiring patterns 25 and an electrical connection is made between the driving IC 7 and the intersubstrate conducting wiring patterns 94 for conduction between the substrates. Since the connections are basically the same in structure, FIG. 9 shows only the electrical connection between the driving IC 7 and the wiring patterns 25 in the IC mounting region 70. Illustration and description of the electrical connection between the driving IC 7 and the intersubstrate conducting wiring patterns 94 are omitted.
In FIG. 9, the IC mounting region 70 and the flexible wiring board connecting region 80 are connected by wiring patterns 9 formed simultaneously with formation of the driving electrode patterns 25. The ends of the wiring patterns 9 placed in the IC mounting region 70 form multiple first terminals 91 (a first terminal group), and are connected to multiple first electrodes 71 (a first electrode group) formed on the active surface of the driving IC 7. The ends of the wiring patterns 9 placed in the flexible wiring board connecting region 80 form multiple second terminals 92 (a second terminal group), and are connected to a second electrode group (not shown) formed on the flexible wiring board 8 (see FIGS. 1, 2, and 3).
Among the plural wiring patterns 9 (9A, 9B, 9C, and 9D), the wiring patterns 9A, 9B, and 9C for supplying voltages, such as a ground potential Vss and a high-voltage potential Vdd, from the flexible wiring board 8 to the driving IC 7 are provided, in the IC mounting region 70, with first terminals 91A, 91B, and 91C which are solid and even wider than a first terminal 91D formed at the end of the wiring pattern 9D. Some of the first electrodes 71 of the driving IC 7 are collectively and electrically connected to each of the terminals 91A, 91B, and 91C. Similarly, the wiring patterns 9A, 9B, and 9C are provided, in the flexible wiring board connecting region 80, with second terminals 92A, 92B, and 92C which are solid and much wider than a second terminal 92D formed at the end of the wiring pattern 9D, and some of the second electrodes of the flexible wiring board 8 are collectively and electrically connected to each of the terminals 92A, 92B, and 92C.
Since the distance between the adjoining electrodes is considerably short, such electrical connections are generally made by using an ACF (Anisotropic Conductive Film). In a mounting method using the anisotropic conductive film, as shown in FIG. 10(A), first, an anisotropic conductive film 6 is applied to the IC mounting region 70, or a sheet-like anisotropic conductive film 6 is placed on the IC mounting region 70. Subsequently, the first electrodes 71 of the driving IC 7 are aligned with the first terminals 91 formed on the second transparent substrate 20. In this state, the driving IC 7 is heated and press-bonded to the second transparent substrate 20 by a head 60, as shown in FIG. 10(B). As a result, a resin component 61 contained in the anisotropic conductive film 6 is melted, and conductive particles 62 contained in the anisotropic conductive film 6 are crushed between the first terminals 91 and the first electrodes 71, as shown in FIG. 10(C). For this reason, the first terminals 91 and the first electrodes 71 are electrically connected via the conductive particles 62, and the driving IC 7 is fixed on the second transparent substrate 20 in a state in which the resin component 61 contained in the anisotropic conductive film 6 is hardened.
As shown in FIG. 9, the second transparent substrate 20 is provided with the electrode patterns 25 for supplying signals output from the driving IC 7 to pixels. The ends of the electrode patterns 25 placed in the IC mounting region 70 form multiple third terminals 93 (a third terminal group). Multiple third electrodes 73 (a third electrode group) formed on the active surface of the driving IC 7 are electrically connected to the third terminals 93. Since the electrical connection in this portion is made simultaneously with the process described with reference to FIG. 9 and the manner thereof is similar to that described with reference to FIG. 9, description thereof is omitted. A method for electrically connecting the flexible wiring board 8 to the flexible wiring board connecting region 80 of the second transparent substrate 20 is nearly similar to that described with reference to FIG. 9. Therefore, description thereof is also omitted.
In such a mounting structure using the anisotropic conductive film 6, mechanical strength of the mounting section is governed by the adhesive force of the resin component 61 contained in the anisotropic conductive film 6. In the conventional mounting structure, when the first terminals 91 formed on the second transparent substrate 20 and the first electrodes 71 formed on the driving IC 7 are reduced in size, the mechanical strength therebetween is significantly decreased.
With such problems in view, an object of the present invention is to provide an IC mounting structure in which mechanical strength of a mounting section using an anisotropic conductive film can be increased by improving the structure of terminals for IC mounting, an electro-optical device, and an electronic apparatus.